... or not, since the cause of the cold or flu is a virus, on which home remedies have no effect. jno's advice is the most sound... don't hold hands, don't kiss, don't occupy the same house if possible. Don't rub your eyes or pick your nose, since these are the two most common ways of transmitting the virus.
As was said prviously, you may not catch this particular strain of virus if you became infected previously. Once a person is infected with the type of virus going around at the moment, the infectee will enjoy lifelong immunity to that particular strain. Problem is, most people catch 1 or 2 colds per year and there are an estimated 275 or so known, non-mutated cold virus'... same thing for flu...
If the boyfriend has had the cold and you've been around him, chances are you're gonna catch it anyway... Sorry...